Conventionally, a rotary electric machine including a rotor disposed rotatably, a stator core having a plurality of slots arranged in a circumferential direction and disposed facing the rotor in a radial direction, and a stator winding wound around the slots of the stator core is generally known as a rotary electric machine used by being mounted on a vehicle.
Then, a stator winding with three-phase (U-phase, V-phase, W-phase) phase windings that each has partial windings electrically connected in double parallel connected in a star connection is disclosed in Japanese Patent Application Laid-Open Publication No. 2010-11623.
Further, the Publication '623 discloses that ends of each partial winding are connected with neutral wires.
In this case, as shown in FIG. 11, among each phase winding connected in double parallel, ends of the two partial windings of the same phase are electrically connected to ends of the neutral wires 26, 27.
Further, in general, a wire having the same cross-sectional area as the partial windings (the same conductor material) is employed for the neutral wires 26, 27.
As the stator winding disclosed in the Publication '623, when the ends of the two partial windings of the same phase are connected to the ends of the neutral wires 26, 27, twice as much current as each of divided windings flows in each of the neutral wires 26, 27.
For example, when the current flows to the V-phase windings from the U-phase windings, assuming i is a current that flow through each partial winding (U1, U2, V1, V2), the current of 2i flows through the neutral wires 26, 27.
Thereby, insulating coatings that surround the outer peripheral surfaces of the neutral wires 26, 27 may be melted due to the temperature of the neutral wires 26, 27 rising excessively, and there is a possibility that insulation failure occurs.
The same problem applies when the current flows in an opposite direction from the V-phase windings to the U-phase windings, between the V-phase windings and W-phase, or between the W-phase windings and the U-phase.